Board Thread:Pokémon Help/@comment-25235588-20180327131313/@comment-27876799-20180327135340

The chance of any wild Pokémon to have its HA, including Legendary Pokémon (set encounter or roaming), is 1/512 with Ability Charm. For Pokémon obtained through breeding, it is 1/256 (1/512 without gamepass).